Amiga International gave them the rights to sell it, basically. It's on wikipedia and other places, so I'm pretty sure it's legit, though there's something with another company also owning some of the rights... (And an alternative, mostly compatible OS called AROS.)
They are giving you WinUAE behind a frontend. Most, but not all amiga emulators are in some way descended from UAE, and a lot of people use WinUAE or FS-UAE, which is apparently easier to use. (Or running on a Raspberry PI, you might want something more specialized for that.)
Don't necessarily know the most about it, though. I watched a few videos, got a copy, had a fun time emulating an Amiga for a bit, then got sidetracked, and didn't quite get back to it...